JPH10130198A - Purification method of acyl chloride - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily obtain a high quality acyl chloride free from troubles such as foreign matters or color by decomposing the reaction product of an amide compound with phosgene in the acyl chloride and subsequently removing the produced amine compound from the acyl chloride. SOLUTION: This method for purifying an acyl chloride comprises reacting an amide compound (e.g. dimethylformamide or dimethylacetamide) and a carboxylic acid (e.g. stearic acid, 2-ethylhexanoic acid) with phosgene, and subsequently pyrolyzing the reaction product of the amide compound with the phosgene in the obtained acyl chloride at a temperature below the decomposition temperature of the reaction product and above the decomposition temperature of the acyl chloride (usually at 50-150 deg.C) for 30min to 10hr, and subsequently removing the produced amine compound preferably by the utilization of a difference between the boiling points of the amine compound and the acyl chloride.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for purifying an acyl chloride.

[0002]

2. Description of the Related Art Acyl chloride is a highly reactive acylating agent and is a useful substance in the chemical industry. Usually, it is produced by chlorinating a carboxylic acid using a chlorinating agent such as thionyl chloride, phosphorus trichloride, phosphorus pentachloride, phosphorus oxychloride, phosgene and the like.

Although chlorinating agents other than phosgene are available at low cost, they are suitable for simple production in a laboratory. However, since sulfur oxides and phosphorus oxides are produced as by-products, they are environmentally friendly from the viewpoint of product purity. It is not suitable as a production method on an industrial scale from the aspect.

On the other hand, phosgene as a chlorinating agent is only hydrogen chloride and harmless carbon dioxide, which are easily harmful by-products, and has great industrial merit that the production cost is low. When chlorinating with phosgene, an amide compound such as dimethylformamide is usually further used. This amide compound reacts with phosgene to produce Vilsm.
It forms an active complex called an eier (Vilsmeier) type complex, which is thought to promote chlorination.

[0005]

The method for producing an acyl chloride by reacting an amide compound, a carboxylic acid and phosgene involves a method in which a foreign substance derived from an amine compound which is a decomposition product of the aforementioned Vilsmeier-type complex is mixed, There was a problem that hue deteriorated. It is difficult to completely remove the foreign matter by a normal filtration operation.

Further, in order to recover the deteriorated hue, purification by distillation is possible, but a distillation facility is required.
Also, depending on the type of acyl chloride, it is thermally decomposed during distillation,
Since the pure content may decrease, it cannot be said that it is an easy purification method.

[0007]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a method for purifying an acyl chloride obtained by reacting an amide compound, a carboxylic acid and phosgene is provided. Thermal decomposition of a reaction product of the amide compound and phosgene to form an amine compound,
This is a method for purifying an acyl chloride, which comprises removing the generated amine compound from the acyl chloride.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The reaction temperature of an amide compound, a carboxylic acid and phosgene is usually in the range from the melting point of the carboxylic acid to the melting point of the carboxylic acid + 50 ° C.
The range from the melting point of the carboxylic acid to the melting point of the carboxylic acid + 20 ° C. or less is more preferably employed.

The use ratio of phosgene to carboxylic acid is selected from a range in which phosgene is excessive relative to carboxylic acid. The ratio of the amide compound to the carboxylic acid is preferably in the range of 0.1 to 10% by weight, more preferably 0.5 to 5% by weight, based on the carboxylic acid.

The acyl chloride obtained by the reaction of an amide compound, a carboxylic acid and phosgene includes a Vilsmeier type complex which is a reaction product of an amide compound and phosgene.

The Vilsmeier-type complex is then decomposed gradually to produce a corresponding amine compound and hydrogen chloride, and the hydrochloride, which is a reaction product of the amine compound and hydrogen chloride, is considered to be a foreign substance in the acyl chloride. Further, it is considered that a reaction product of a trace amount of phosgene in the acyl chloride and the amine compound becomes a coloring component in the acyl chloride.

According to the present invention, an amine compound is produced by thermally decomposing a Vilsmeier type complex in an acyl chloride obtained by a reaction of an amide compound, a carboxylic acid and phosgene,
The purpose is to remove the generated amine compound in advance. Thereby, generation of the foreign matter and the coloring component can be avoided.

The amide compound in the present invention is selected from those capable of forming a Vilsmeier type complex by reacting with phosgene. The Vilsmeier-type complex reacts with a carboxylic acid under chlorination reaction conditions to give the desired product, acyl chloride.

As the amide compound to be used, a compound in which the boiling point of the amine compound formed by thermal decomposition of the Vilsmeier type complex is lower than that of the acyl chloride is preferable. From such a viewpoint, as the amide compound, dimethylformamide (DMF), dimethylacetamide, N-methylformamide, N-methylacetamide and the like are preferable.

The carboxylic acid used as a raw material for the acyl chloride is not particularly limited as long as it produces the corresponding acyl chloride by the action of an amide compound and phosgene, and is not limited to a monofunctional carboxylic acid or a difunctional or higher polyfunctional carboxylic acid. Various carboxylic acids selected from acids can be used.

For example, saturated aliphatic acids such as caproic acid, caprylic acid, 2-ethylhexanoic acid, pivalic acid, 2,2-dimethyloctanoic acid, nonanoic acid, lauric acid, myristic acid, palmitic acid, stearic acid, and behenic acid Unsaturated aliphatic carboxylic acids such as carboxylic acid, acrylic acid, methacrylic acid, oleic acid, linoleic acid, linolenic acid, and erucic acid; aromatic carboxylic acids such as benzoic acid, toluic acid, and naphthic acid; phenylacetic acid; phenylpropionic acid Aliphatic carboxylic acids having an aromatic group such as maleic acid,
Examples include bifunctional carboxylic acids such as succinic acid, adipic acid, phthalic acid, isophthalic acid, and terephthalic acid. These carboxylic acids are used as one kind or as a mixture of two or more kinds.

The thermal decomposition of the Vilsmeier type complex is usually carried out at a temperature not lower than the decomposition temperature of the Vilsmeier type complex and lower than the decomposition temperature of the acyl chloride. If the temperature is too low, it is not preferable because the thermal decomposition is insufficient or the thermal decomposition takes a long time. If the temperature is too high, the target acyl chloride is scattered outside the system, which is not preferable.

Although the thermal decomposition temperature of the Vilsmeier type complex depends on the amide compound used, it is usually 50 to 150 ° C.
Preferably it is 70-140 degreeC, More preferably, it is 80-1.
00 ° C.

The time for the thermal decomposition may be appropriately selected according to the amount of the acyl chloride, the amount of the amide compound and the like. If the time is too short, the effect of the present invention cannot be obtained due to insufficient decomposition of the Vilsmeier-type complex, and if the time is too long, it is economically disadvantageous and the acyl chloride may be decomposed. Therefore, about 30 minutes to 10 hours are preferable.

In order to quickly remove an amine compound which is a thermal decomposition product of a Vilsmeier type complex from a reaction product containing an acyl chloride obtained by reacting an amide compound, a carboxylic acid and phosgene, an amine compound and an acyl chloride are required. Is preferred.

For example, a method in which the inside of the reaction system is kept at a temperature higher than the boiling point of the amine compound and lower than the boiling point of the acyl chloride, and an inert gas such as nitrogen is blown into the reaction system to extract the amine compound out of the reaction system. No. In this method, the pressure inside the reaction system may be reduced instead of blowing the inert gas into the reaction system, or simultaneously with blowing the inert gas. Further, the amine compound in the acyl chloride may be separated by a usual distillation operation.

[0022]

【Example】

"Example 1 (Example)" 568 g in a 1-liter flask
(2 mol) of stearic acid and 5 g of dimethylformamide were charged, and 218 g (2.2 mol) of phosgene was blown at 80 ° C. over 2 hours to obtain a chlorination reaction product.
By raising the temperature to 90 ° C. while blowing nitrogen into the reaction product and maintaining the temperature for 8 hours, components lower in boiling point than the target product stearoyl chloride were removed to obtain the target product.

The desired product was 99.0 by gas chromatography analysis.
% Of stearoyl chloride. Further, the appearance was pale yellow and transparent, no foreign matter was observed, and the Gardner chromaticity was 7. The desired product was stored in a glass bottle at room temperature.
There was no change after months.

Example 2 (Comparative Example) Instead of raising the temperature to 90 ° C. while blowing nitrogen, 2
The procedure was performed in the same manner as in Example 1 except that the temperature was lowered to room temperature over time. As a result, it was confirmed by gas chromatography that the obtained target product was stearoyl chloride having a purity of 99.0% or more. The appearance was pale yellow and transparent, no foreign matter was observed, and the Gardner chromaticity was 5.

When this target product was put in a glass bottle and stored at room temperature, precipitation of white precipitated foreign matter was observed after one week. When this white foreign substance was identified by mass spectrum analysis, it was found to be dimethylamine hydrochloride.

Example 3 The reaction was carried out in the same manner as in Example 1 except that 2-ethylhexanoic acid (316 g, 2 mol) was used instead of stearic acid, and a reaction product containing 2-ethylhexanoyl chloride was used. I got The temperature of the reaction product was raised to 95 ° C. while blowing nitrogen into the reaction product and maintained for 4 hours, and then distilled under reduced pressure to obtain a fraction 342 of 90 to 95 ° C. at 20 mmHg.
g was obtained (97% yield).

This fraction was 99.7% by gas chromatography analysis.
It was confirmed to be 2-ethylhexanoyl chloride having the above purity. Further, the appearance was colorless and transparent, no foreign matter was recognized, and the APHA chromaticity was 5. No change in appearance was observed even after storage at room temperature in a glass bottle for 6 months.

Example 4 (Comparative Example) Instead of raising the temperature to 95 ° C. while blowing nitrogen, 2
The same procedure was performed as in Example 3 except that the temperature was lowered to room temperature over time. As a result, the obtained target product was confirmed by gas chromatography to be 2-ethylhexanoyl chloride having a purity of 99.6% or more. Further, the appearance was colorless and transparent, no foreign matter was recognized, and the APHA chromaticity was 5.

When the target product was put in a glass bottle and stored at room temperature, precipitation of white foreign matter was observed after 10 days. When this white foreign matter was identified by mass spectrum analysis, it was found to be dimethylamine hydrochloride.

[0030]

According to the method of the present invention, a high-quality acyl chloride having no problems such as foreign matter and coloring can be obtained.

Claims (2)

[Claims] In a method for purifying an acyl chloride obtained by reacting an amide compound, a carboxylic acid and phosgene, a reaction product of the amide compound and phosgene in the acyl chloride is thermally decomposed to produce an amine compound. A method for purifying acyl chloride, comprising removing an amine compound from acyl chloride. 2. The method according to claim 1, wherein the thermal decomposition is carried out at a temperature not lower than the decomposition temperature of the reaction product of the amide compound and phosgene and lower than the decomposition temperature of the acyl chloride.